Last week, the House Science, Space and Technology committee invited four witnesses from NASA’s past to discuss the agency’s future endeavors, including a human mission to Mars, a possible return to the moon, and the commercial space sector. NASA consistently polls as Americans’ favorite federal agency, and its popularity cuts across party lines. The hearing could have been a brief respite from the bickering that has seized Washington of late. And it almost was.

Near the end, Ellen Stofan, NASA’s chief science officer under President Barack Obama, gave Mars enthusiasts some reason for hope. Americans can expect a lunar habitat by the 2020s and humans in Mars orbit in 2032, she said.

That’s the clearest timeline on NASA’s “Journey to Mars” in some time. Many space enthusiasts were, well, enthused. But then last Friday, Stofan shared this picture:

Where was she? Missing from more than the photo, it turned out. The House committee’s Twitter account—the same one that has shared false climate-change information from Breitbart News—didn’t mention her at all in its tweets covering the hearing.

The account posted 10 tweets total about the hearing, including a link to a video feed of the testimony. It shared sound bites from each of the panel’s other three witnesses: Harrison Schmitt, an Apollo 17 astronaut and former U.S. senator from New Mexico; Lt. Gen. Thomas Stafford, an astronaut on Apollo 10 and two Gemini missions; and A. Thomas Young, who was the mission director for the Viking Mars program and a former director of Goddard Space Flight Center in Greenbelt, Maryland.

“There must be a permanent public and political commitment to deep-space exploration and development,” the account quoted Schmitt saying.

It also quoted Representative Lamar Smith of Texas, the committee’s chair, and Representative Brian Babin of Texas, whose district includes NASA’s Johnson Space Center, talking about American leadership in space. If you’d read that feed for coverage of the two-and-a-half-hour hearing, you’d be forgiven for thinking Stofan didn’t show up at all.

But she testified at length. She gave detailed answers to numerous questions about the space agency’s Earth science mission, about NASA’s Mars trajectory, about human space exploration, and plenty of other topics, many of intense public interest. It was curious that she didn’t appear at all in the committee’s Twitter feed.

I called the committee’s offices to ask about this omission. The person who answered the phone Friday paused and said, “that’s a good question,” before referring me to the communications staff. At the time of publication, I had not heard back.

Stofan was nonplussed, both on Twitter and on the phone from her vacation home in North Carolina last weekend.

“I understand that it’s probably mostly because they are the Republican witnesses. I was invited by the minority party, the Democrats. But the optics of being the only woman…,” she trailed off, with a rueful laugh. “You know, I understand, that’s the way the system works. I hope we’re turning away from that system.”

Stofan was referring to the systemic mistreatment of women in science, as supported by a  wealth of scientific papers in academic journals, which speak to the persistence of sexism, ossified gender roles, the prevalence and endurance of bias, and the underrepresentation of women (especially women of color). This body of research demonstrates the detrimental effect of these biases on Ph.D.s, salaries and careers and the importance of representatives and role models.

For these reasons and others, Stofan’s omission prompted an outcry. “Don’t ask questions about encouraging young people to get into STEM and then make it look like it's only for old white guys,” one woman wrote to Stofan. “As a woman seeking a STEM career, for that matter a human who cares about science ... this bewilders me,” said another.

In this context, it’s worth noting the last tweet posted prior to the committee hearing. It highlighted the INSPIRE Act, a one-page bill that authorizes the NASA administrator to “facilitate and support … early-career female astronauts, scientists, engineers, and innovators to engage with K–12 female STEM students and inspire the next generation of women.” This is an admirable goal, and worthy of the committee’s support.

Of course, it’s possible that Stofan’s omission was unintentional, and an honest mistake. In our conversation, Stofan took great pains to praise the committee staff, saying they were all pleasant and welcoming, and she stressed that the questions from members of Congress were friendly and curious.

But it’s also worth noting that Stofan was the only witness who has worked at NASA recently. After leaving Goddard many years ago, Young spent two decades as the CEO of Martin Marietta and later Lockheed Martin. After losing his reelection in the Senate, Schmitt worked as a consultant and led an effort to encourage private companies to mine the moon. In 2008, he abruptly quit the Planetary Society because of disagreements over its Mars advocacy and its statements about a scientific consensus on climate change, which he said was “ridiculous.” As for Stafford, he worked for President Ronald Reagan as a defense advisor and later chaired a committee to carry out President George H.W. Bush’s ambitious but short-lived Mars plan, before chairing the International Space Station Advisory Committee.

Stofan, on the other hand, served as chief scientist from 2013 until the inauguration. Previously, she spent 13 years as a planetary-geology professor and worked in the private sector as a research scientist. Before that, she spent a decade at the Jet Propulsion Laboratory. Stofan is the only witness to have worked at NASA since the 1980s.

“It was a little frustrating to me that they were people who hadn’t been involved in the agency in a long time, and in some cases weren’t entirely up to date on what’s going on,” Stofan said. “When you’re talking about the future of NASA, you’d want to hear someone who was more recently involved.”

In discussing her disappointment, Stofan quoted Sally Ride, the first American woman in space and a personal hero to many children of the space age, who said shortly before she died in 2012, “You can’t be what you can’t see.”

“If we turn a blind eye, or don’t show that women are there, what are we telling people about how women are valued?” Stofan told me. “What are we telling girls about their ability to go into different careers? The message it sends to women is not a great one.”